A Study On Process Of Direct Reduction Of Pellets Made From Concentrate Based On Coal Gasification

Our country is rich in coal resources, clean-coal gasification process are more mature, so many researchers’attention focus on process of coal gasification—direct reduction. This paper is a study on process of direct reduction of pellets made from concentrate based on coal gasification. The main conclusions are as follows。The effect of types and dosage of binder on green ball making pellet, preheating roasting concretion and direct reduction have been studied systemically. It was shown that the quality of bentonite preheating pellets is better than F binder pellets; the strength of F binder green pellets is better than the bentonite pellets. In the gas reduction stage, the compressive strength of ruduction pellet can be improved by using F binder as binder.Along with the increase of preheating temperature, the compressive strength of preheating pellets improved, the reduction rate was slower, the compressive strength of reduction pellets increased. Using hot pellet added1.5%bentonite as reduction burden, reduction for lmin, the the compressive strength of preheating pellets declined by79.6%, the minmum compressive strength was214Newton per pellet during the reduction process. Using hot pellet added1.5%F binder as reduction burden, the compressive strength of preheating pellets declined by66.1%, the minmum compressive strength was494Newton per pellet during the reduction process,it is obvious better than bentonite pellet.The thermodynamics and isothermal kinetics of reduction of pellets with F binder and the re duction behavior were investigated respectively. Results show that the reduction model of F binder pellets is porous volume reaction model. Because the reaction speed is fast, at the initial stage of reduction, crystal trasfoformation,the volme expansion, pellet strength falling rapidly. Reduction for lmin compressive strength decreased by64%--80%, with the generation of iron, the compressive strength of reduction pellet increased. In this paper, compression strength variation rule and improve method were studied by using preheated pellets with and without cooling as the burden. The result shows that in the case of equal added binder, the compressive strength of reduced pellets via thermal charging improves obviously; with addition of the binder the compression strength of reduced pellets increases. The reduction speed of thermal charging is slower than the cold-one. Using the preheated pellets without cooling as the burden can promote the accumulation of the iron crystal grain, so the compressive strength is higher than cold-one.